U.S. Secretary of State John Kerry, British Foreign Secretary Philip Hammond, Russia's Foreign Minister Sergei Lavrov and Iranian Foreign Minister Mohammad Javad Zarif (L to R) pose for photos prior to a to a closed-door meetings of nuclear talks at Palais Coburg, the venue of nuclear talks in Vienna, Austria, Nov. 24, 2014. The parties involved in Iran's nuclear talks may consider extension of the negotiation if time is not enough for a deal, Chinese Foreign Minister Wang Yi said here on Monday. (Xinhua/Zhang Fan)